One of the largest supermarket chains in the country is resisting calls from farmworkers and food activists to pay a penny more per pound of tomatoes as part of an agreement that would raise wages and improve working conditions for tomato pickers.

Eleven national corporations — including Burger King, Taco Bell, and food-services giant Aramark — participate in the Fair Food partnership to pay a premium and promise to protect worker rights.

But the supermarket industry — save Trader Joe's and Whole Foods — has been largely absent from the collaboration.

The Coalition of Immokalee Workers has tried for years to bring Publix on board, but the largest employee-owned grocery chain in the country said it won't get involved in what it calls "a labor issue."

"We believe in the dignity and respect of all people," said spokesman Dwaine Stevens. "We'll pay [the extra penny]; just put it in the price."

But the extra penny isn't the only thing they want from Publix. Activists want the giant grocer to sign the worker-protection agreement.

That will ensure it will purchase tomatoes from approved growers and use its purchasing power to put pressure on suppliers to treat workers fairly.

"Publix is the No. 1 supermarket in Florida, and it can set an example for other companies," said farmworker and organizer Oscar Otzoy. "It's an offense to us and our progress for them to describe this as simply a labor dispute."

Otzoy said he has seen systematic changes since his organization convinced the Florida Tomato Growers Exchange — representing 90 percent of the state's tomato industry — to sign the agreement. But organizers realized they needed to target the retailers for a permanent change.

Farmworkers now use timecards to record their hours and are encouraged by their employers to report any abuses they experience while on the job without fear of retribution. Sexual assault is a particular problem for female farmworkers, he said.

"When you have a family problem, you sit down and talk about as a family," Otzoy said, who was part of a delegation Saturday that delivered a petition to Publix store manager Paul Bracker. "They don't want to talk to us."

Stevens said Publix has never met with the farmworkers and has no plans to do so.

With the help of from local church congregants, community groups and the national civil-rights organization International Justice Mission, Otzoy asked Bracker to be his voice to facilitate dialogue.

"I think it's good that you came here to help us understand," Bracker said, surrounded by protesters. "I'm glad that you came to our store."

Saturday's demonstration comes one month before the farmworkers expect to march from Fort Myers to Publix headquarters in Lakeland.